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meetings / 140401_webex_6top

Minutes Webex 1 April, 6top call 6TiSCH WG

Note: timestamps in PDT.

Taking notes (using Etherpad)

  1. Xavi Vilajosana
  2. Thomas Watteyne
  3. Raghuram Sudhaakar

Attendance (alphabetically)

  1. Pouria Zand
  2. Qin Wang
  3. Raghuram Sudhaakar
  4. Thomas Watteyne
  5. Xavi Vilajosana

Action items

  • Raghuram and Pouria to indicate on ML the maximum length of payload.
  • Qin to investigate the possibility of doing 6top-to-6top negotiation using CoAP
  • Qin to start Doodle to find good time for next calls.
  • Thomas to publish minutes on ML.


  • [08.05] meeting starts
  • [Qin] in draft-sudhaakar-6tisch-coap-01, what is the difference management and information resources?
  • [Raghuram] management is R/W, information is R-only. Categorization based on this.
  • [Raghuram] URL are generated by following YANG data model. See example.
  • [Raghuram] let's use this call to discuss basic direction we want the discussion to progress.
  • [Raghuram] how are we going to reuse CoAP parser. Clarify the reason to choose between CoAP and 6top-to-6top.
  • [Pouria] clarify exactly what are the requirements to 6top-to-6top communication.
    • Example: is there any case when the parent needs to monitor children or keep its connection? maybe different requirements/methods
  • [Raghuram] we need to differentiate 6top-to-6top and PCE-based monitoring and management, in particular access control. security will be affected.
  • [Thomas] Number of things to take in to account.
    • what to do about security (in particular Authentication and Authorization)
      • make use of what is happening in DICE and ACE?
    • what to do when the payload is too long?
      • Block transfer?
    • do we want/need observe mechanism?
      • Observe is inherent CoAP - make it part of 6top-to-6top?
  • [Thomas] About footprint, CoAP implementation might be shared between L2 and L7.
  • [Qin] is this also related to 6top to 6top communication or it is also related to PCE to 6top communication?
  • [Raghuram] We see lots of similarities between both cases. -> Reuse?
  • [Thomas] if we have the real CoAP implementation from L7, most of the handling of it can be deferred to that layer. In the implementation they will use the same functions.
    • Assuming that at layer 7 we have all this pieces this does not increment the footprint.
  • [Raghuram] what are the boundaries of what will go inside of the mote.
  • [Qin] 2 different approaches
    • Check if coap can live inside 6top
    • take everything from CoAP.
  • [Pouria] Classify 6top to 6top communication in 2 classes:
    • requiring lots of bytes to be transferred --> back-call to l4 to do that instead of 6top
  • [Raghuram] Identify What are the other elements that CoAP also offers that can be beneficial for us.
  • [Thomas] ACE WG is working on security aspects.
  • [Raghuram] Include a field that ACE can use inside the Wrapper IE to support authorization.
  • [Thomas] Length of packet might be a problem, what is the longest payload we expect?
  • [Raghuram] With current version of CoAP draft, payload is short. Not exceeding 200B.
  • [Thomas] If it is longer to what we can fit into an IE, we will require fragmentation. Block transfer can be used for that.

    Action item: Raghuram and Pouria to indicate on ML the maximum length of payload.

  • [Thomas] Other important point is negotiation between 6top peers.
    • In draft-wang-6tisch-6top-sublayer-00, sublayer draft proposes a negotiation format.
    • Do we want to/can we add negotiation as part of the data model?
  • [Qin] Question about whether to use separate negotiation protocol or use coap as well:
    • this will enable to represent negotiation messages as part of the data model
    • differentiation between accessing MIB and negotiation
  • the content of what goes over the air in a negotiation process
    • negotiation packet is not part of the data model, is more an extension to the transport protocol (CoAP),
    • evaluate if it is possible to define the message content as part of the YANG model or in contrast think on how to extend CoAP to have that message format.
    • CoAP enables RESTful interface through GET, PUT, POST, DELETE methods
  • POST enables invoke

    Action item: Qin to investigate the possibility of doing 6top-to-6top negotiation using CoAP

  • 6top-to-6top communication might be limited by authority part defined by CoAP as this requires IP addresses of counterparts.
  • [Qin] Next call, at what time? We will have people calling in from China, PDT and CET>

    Action item: Qin to start Doodle to find good time for next calls.

  • AOB

    Action item: Thomas to publish minutes on ML.

  • [08.58] meeting ends